<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <script>
    let a = +prompt("请输入一个数字");
    let b = parseInt(prompt("请输入一个数字"));

    let c = a + b
    alert(c);12
    </script>



</body>
</html>